1. Field of the Invention
The present invention relates to a magnetic recording medium. More particularly, it relates to a magnetic recording medium which imparts satisfactory repeat running durability and mechanical strength as adhesive strength. The present invention also relates to a composition of binders for a magnetic recording medium which imparts excellent repeat running durability without losing the adhesive strength in the preparation of a magnetic recording medium having a thin thickness as a cassette magnetic recording medium.
2. Description of the Prior Art
The magnetic recording medium usually prepared by coating a magnetic powder composition comprising a magnetic powder and a binder on a substrate such as film made of polyacetate, polyvinyl chloride or polyester to form a magnetic layer on the substrate.
Recently, the usages of the magnetic recording medium has been expanded and higher characteristics have been further required. For example, the recording time could be prolonged by using a magnetic recording tape having longer length and thinner thickness. Recently, it has been succeeded to prepare a magnetic recording medium having a polyester base film having a thickness of 5 to 6.mu. and a magnetic layer having a thickness of 3 to 4.mu. as a thinner tape. In the magnetic recording tape, the film base as the substrate is thin whereby the mechanical strength is inferior and one side elongation or certain bending is easily caused by repeat running of the magnetic recording tape and certain abnormal running is caused to prevent normal recording and reproduction which are important and indispensable for the magnetic recording medium. Consequently, it is sometimes difficult to use such films.
On the other hand, in order to prevent such disadvantages, it has been studied to improve both the base film and the coated magnetic layer. Various improvements of strength of the base film have been studied. However, a satisfactory result has not been attained from the viewpoint.
In view of the problems of the conventional technology, it has been studied to improve the magnetic layer of the magnetic recording medium and to increase the mechanical strength and to impart excellent stable function for recording and reproduction by improving the binder incorporated in the magnetic layer.
Various studies have been made to overcome the disadvantages depending upon the magnetic layer of the conventional magnetic recording medium.